Identification of Riparian Zone Encroachment Using Remote Sensing and Gis Techniques

The 40th Asian Conference on Remote Sensing (ACRS 2019) October 14-18, 2019 / Daejeon Convention Center(DCC), Daejeon, Korea TuP-43 IDENTIFICATION OF RIPARIAN ZONE ENCROACHMENT USING REMOTE SENSING AND GIS TECHNIQUES Mary Grace A. Loberiano (1), Roxanne I. Mabunga (1), Edgardo G. Macatulad (1) 1 Department of Geodetic Engineering, College of Engineering, University of the Philippines Diliman, 1101, Quezon City, Philippines Email: [email protected]; [email protected]; [email protected] KEY WORDS: water easements, geoprocessing model, PlanetScope, Ampid River ABSTRACT: Riparian zones are areas that exist between terrestrial and aquatic ecosystems consisting of vegetation and soils of higher slope grade. They are important in protecting aquatic ecosystems when water level rises, in supporting a diverse set of vegetation, and in making considerations for land use management. For the protection of these areas, the Philippines’ Water Code (Article 51) states that easements along rivers should be defined and shall not have any human activity that may destroy the natural biodiversity in the area. Considering how important these areas are, identifying them should be among the priority tasks of the local government. However, this can be tedious and expensive because traditional techniques use field-based methods. In this paper, a geoprocessing model for the identification of the riparian zone of a river system and the encroachment within these areas was developed. The model was implemented in the Ampid River, located in San Mateo, Rizal, Philippines. The framework of the processing model is based on remote sensing and Geographic Information Systems (GIS) principles. Remote sensing was used to classify PlanetScope Ortho Analytic Scene satellite images from three consecutive years, 2016 to 2018. Supervised classification was used to classify the images into different land cover types wherein the annual crops and built-up areas were assigned to represent agricultural and urban development areas in the riparian zone. The GIS model was used to identify and map the riparian zone and to evaluate the area encroached using the buffer distances based on the land cover type. The resulting total encroachment areas of built-up areas for both banks for a 3-meter urban buffer were 13,309.62 sqm for 2016, 14,942.70 sqm for 2017 and 11,910.42 sqm for 2018. Using the 20-meter agricultural buffer, the encroached areas by annual crops for 2016, 2017 and 2018 were 63,944.72 sqm, 96,147.55 sqm, and 86,033.82 sqm respectively. Linear regression was performed on these images to create a general linear projection of the encroachment to predict the possible area encroached for the succeeding two years. 1. INTRODUCTION 1.1 Background The Philippine archipelago is among the countries in the Pacific visited by an average of 20 typhoons per year (Asian Disaster Reduction Center, 2013). In 2018, there have been 21 storms, typhoon Usman being the last one entering the Philippine waters on December 25, 2018 (Yap, 2018), with accompanying rains affecting the country until the midnight of January 1, 2019. Aside from typhoons, the country is also affected by rains brought about by the Southwest Monsoon, also known as hanging Habagat. These storms and torrential rains bring forth floods in areas that are prone to soil erosion and areas that are badly managed, especially populated areas alongside the rivers, which puts lives at risk to landslides and floods. Riparian zones are ecosystems existing between aquatic and terrestrial ones and are surrounded by much drier soils with higher slope grades. They are important in making considerations for land use and management as well as in protecting aquatic ecosystems by “removing sediments from surface runoff, decreasing flooding, maintaining appropriate water conditions for aquatic life, and providing organic material vital for productivity and structure of aquatic ecosystems.” Moreover, they are also considered home for wildlife providing water source, food, and shelter (Machtinger, 2007). In general, riparian zones or corridors are important because they are the most fertile part of the area that can support a diverse set of vegetation and are also the first line of defense when water level rises in the aquatic ecosystem. Riparian zones are prone to degradation and damage especially in areas that are highly urbanized. These damages can affect the ecological and economic productivity of the riparian areas, and worse, it can affect the lives of people living near these areas by putting them at risk of flooding. With this in mind, it is important to account for these damages done in the riparian zones. Performing a large-scale research study on the riparian zones of Philippine rivers will not only be costly, it will also be time consuming considering the number of rivers flowing within the country if traditional field-based methods will be used. Thus, this research aims to develop an alternative way in identifying riparian zones through utilizing 1 Remote Sensing (RS) and Geographic Information Systems (GIS), and through assessing one river at a time. Delineating riparian zone encroachment using a GIS processing model following the Philippines’ Water Code is developed which can help in identifying and understanding how these areas are affected by increasing urbanization. Statistical analysis of the rate of encroachment is also performed to estimate future encroachment scenarios. 1.2 Riparian zones and water easements The Philippine constitution has set rules and regulations through the Water Code in order to preserve our water bodies as well as the areas around them. Article 51 under Chapter IV of The Water Code of the Philippines (Presidential Decree No. 1067) states that the “banks of rivers and streams and the shores of the seas and lakes throughout their entire length and within a zone of three (3) meters in urban areas, twenty (20) meters in agricultural areas and forty (40) meters in forest areas, along their margins are subject to the easement of public use” (Presidential Decree No. 1067, 1976). However, the lack of stringent implementation of the law as well as the lack of knowledge of these guidelines amongst the people living near water bodies both impacts how ecosystems in our rivers and water bodies thrive. This section of the Water Code defines the parameters in which this research will base the buffers to identify the riparian zone of Ampid River. Furthermore, one of the administrative orders of the Department of Environment and Natural Resources (DENR) has solidified the importance of Article 51 of the Water Code in the preservation of biodiversity. In DAO No. 99-21, issued on June 11, 1999 as a response to the geodetic engineering profession’s clamor to ensure the preservation of ecological balance and protection. Strict implementation of Article 51 of PD 1067 was promulgated in the processing, verification, and approval of isolated and cadastral surveys (DAO No. 99- 21, 1999) 1.3 Study Area The province of Rizal, shown in Figure 1, is located in the CALABARZON Region. It is bounded by Metro Manila, Bulacan, Quezon Province, and Laguna to the west, north, east, and southeast respectively (Salonga, 1934). The province is streaked through by a number of rivers notable of which are Angono River, Marikina River, Pasig River, and Taytay River among others. The Province of Rizal is a mountainous region with a total area of 1,191.94 square kilometer and a population density of 2,400/km2; the highest among all the 81 provinces in the country based on the 2015 census (Rizalprovince.ph., 2013). Six rivers passing through the province are tributaries of the Laguna Lake, these are Morong River, Tanay River, Sapang Baho River, Marikina River, Taytay River which intersect with the Mangahan Floodway, and Pasig River (Greenpeace, 2010). Ampid River, which has a length of 11. 48 kilometers and traversing barangays Ampid I, Ampid II, Gulod Malaya, Sto. Niño, and barangay Silangan of San Mateo, will be the focus of this study. It drains the southern hilly areas of Barangays Silangan, Sto. Niño, Gulod Malaya and Ampid and unsafely flows through the populated portions of the municipality. Figure 1. Location of the rivers in San Mateo, Rizal, Philippines 2 2. MATERIALS AND METHODS 2.1 Creation of the riverbank shapefile for Ampid River A DEM of the study area derived from 2013 Airborne Interferometric Synthetic Aperture Radar (IfSAR) was obtained from the National Mapping and Resource Information Authority (NAMRIA). The Terrain Analysis Using Digital Elevation Models (TauDEM) toolbox developed by David G. Tarboton of Utah State University was utilized for the analysis and extraction of hydrologic information from the DEM, specifically, to determine the riverbanks of the Ampid River. The left and right riverbanks are delineated separately as line features. 2.2 Image processing Three 4-band PlanetScope Scene satellite images were downloaded from Planet Labs, with acquisition dates October 2016, 2017, and 2018. These images are already geometrically, radiometrically, and atmospherically corrected, thus may already be used for supervised image classification. Using Maximum Likelihood Classification, the land cover identified were annual crop, brush or shrubs, built-up, grassland, and inland water, based from the 2015 Land Cover of San Mateo. Only one set of ROIs was used for the three images for temporal analysis. The resulting land cover classifications per year are then converted in GIS feature layers for further analysis. 2.3 GIS model for riparian zone encroachment A GIS model was developed using the ModelBuilder feature in ArcGIS 10.3. The model involves getting the classified images and the river boundaries as inputs. These are projected to the Philippine Reference System of 1992 (PRS 92) as prescribed by the mapping authorities in the country, and the land cover is clipped to the extent of the area of interest. Buffers are generated based on the Philippine Water Code: 3-meter for urban areas, 20 meters for agricultural areas, and 40 meters for forest areas.

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